The present invention relates to a method and apparatus to check the state of wear in a coating fabric of a driving belt.
It is well known that for driving belts periodical inspections and/or replacements are required in order to avoid the risk, above all where positive drive belts are concerned, of the mechanical devices or members driving or driven by the belt being damaged, which would occur in case of accidental breakage of the belt itself.
Belts are usually comprised of an elastomeric body and a coating fabric applied to at least one of the belt surfaces designed to come into contact with the active surfaces of the belt pulleys.
In toothed belts this fabric is provided to coat the belt toothing designed to mesh with the pulley teeth.
In many cases the periodical inspection and/or replacements carried out directly by the person utilizing and/or taking care of the machine or apparatus on which the belt is mounted, is not sufficient to avoid the risk of breakage of the belt resulting from the wear of the coating fabric for example.
For the purpose of avoiding this problem, the applicant has developed a method and apparatus capable of checking the acceptability of the state of wear of the coating fabric in a driving belt in a completely automatic manner.
In particular this method and apparatus, being the object of the European Patent Application No. 91830544.2, disclose the use of a driving belt, a toothed belt for example, provided with a reinforcing textile cover applied to the work surface acting in contact with the pulleys.
The covering fabric is treated with electrically conductive charges so that, by applying an electric voltage between two pulleys engaging the belt which are electrically insulated from each other, it is possible to detect the resistance offered to the passage of current by at least two belt branches kept taut between said pulleys.
The belt use brings about the progressive consumption of the electrically conductive charges of the covering fabric and, consequently, the progressive increase in the detectable resistance value, so that, based on the detected resistance value, it is possible to ascertain to the state of wear of the belt fabric.
In particular, the resistance value detected on the belt is provided to be compared with a previously input resistance value corresponding to a given state of wear of the belt fabric.
When the belt fabric resistance overcomes the previously input value, a danger signal is emitted which informs the operator about the necessity of replacing the belt, which operation must be planned in due time in order to avoid the occurrence of irreparable damage not only to the belt but also to the motor to which the belt is connected.